NAME

newsfeeds - determine where Usenet articles get sent

DESCRIPTION

The file /etc/news/newsfeeds specifies how incoming articles should be
distributed to other sites. It is parsed by the InterNetNews server
innd(8) when it starts up, or when directed to by ctlinnd(8).
The file is interpreted as a set of lines according to the following
rules. If a line ends with a backslash, then the backslash, the
newline, and any whitespace at the start of the next line is deleted.
This is repeated until the entire ‘‘logical’’ line is collected. If
the logical line is blank, or starts with a number sign (‘‘#’’), it is
ignored.
All other lines are interpreted as feed entries. An entry should
consist of four colon-separated fields; two of the fields may have
optional sub-fields, marked off by a slash. Fields or sub-fields that
take multiple parameters should be separated by a comma. Extra
whitespace can cause problems. Except for the site names, case is
significant. The format of an entry is:
sitename[/exclude,exclude,...]\
:pattern,pattern...[/distrib,distrib...]\
:flag,flag...\
:param
Each field is described below.
The sitename is the name of the site to which a news article can be
sent. It is used for writing log entries and for determining if an
article should be forwarded to a site. If sitename already appears in
the article’s Path header, then the article will not be sent to the
site. The name is usually whatever the remote site uses to identify
itself in the Path line, but can be almost any word that makes sense;
special local entries (such as archivers or gateways) should probably
end with an exclamation point to make sure that they do not have the
same name as any real site. For example, ‘‘gateway’’ is an obvious
name for the local entry that forwards articles out to a mailing list.
If a site with the name ‘‘gateway’’ posts an article, when the local
site receives the article it will see the name in the Path and not send
the article to its own ‘‘gateway’’ entry. See also the description of
the ‘‘Ap’’ flag, below. If an entry has an exclusion sub-field, then
the article will not be sent to that site if any of the names specified
as excludes appear in the Path header. The same sitename can be used
more than once — the appropriate action will be taken for each entry
that should receive the article, regardless of the name — although this
is recommended only for program feeds to avoid confusion. Case is not
significant in site names.
The patterns specify which groups to send to the site and are
interpreted to build a ‘‘subscription list’’ for the site. The default
subscription is to get all groups. The patterns in the field are
wildmat(3)-style patterns, and are matched in order against the list of
newsgroups that the local site receives. If the first character of a
pattern is an exclamation mark, then any groups matching the pattern
are removed from the subscription, otherwise any matching groups are
added. For example, to receive all ‘‘comp’’ groups, but only
comp.sources.unix within the sources newsgroups, the following set of
patterns can be used:
comp.*,!comp.sources.*,comp.sources.unix
There are three things to note about this example. The first is that
the trailing ‘‘.*’’ is required. The second is that, again, the result
of the last match is the most important. The third is that
‘‘comp.sources.*’’ could be written as ‘‘comp.sources*’’ but this would
not have the same effect if there were a ‘‘comp.sources-only’’ group.
There is also a way to subscribe to a newsgroup negatively. That is to
say, do not send this group even if the article is cross-posted to a
subscribed newsgroup. If the first character of a pattern is an atsign
‘‘@’’, it means that any article posted to a group matching the pattern
will not be sent even though the article may be cross-posted to a group
which is subscribed. The same rules of precedence apply in that the
last match is the one which counts. For example, if you want to
prevent all articles posted to any "alt.binaries.warez" group from
being propagated even if it is cross-posted to another "alt" group or
any other group for that matter, then the following set of patterns can
be used:
alt.*,@alt.binaries.warez.*,misc.*
If you reverse the alt.* and alt.binaries.warez.* patterns, it would
nullify the atsign because the result of the last match is the one that
counts. Using the above example, if an article is posted to one or
more of the alt.binaries.warez.* groups and is cross-posted to
misc.test, then the article is not sent.
See innd(8) for details on the propagation of control messages.
A subscription can be further modified by specifying ‘‘distributions’’
that the site should or should not receive. The default is to send all
articles to all sites that subscribe to any of the groups where it has
been posted , but if an article has a Distribution header and any
distribs are specified, then they are checked according to the
following rules:
1. If the Distribution header matches any of the values in the sub-
field, then the article is sent.
2. If a distrib starts with an exclamation point, and it matches
the Distribution header, then the article is not sent.
3. If Distribution header does not match any distrib in the site’s
entry, and no negations were used, then the article is not sent.
4. If Distribution header does not match any distrib in the site’s
entry, and any distrib started with an exclamation point, then
the article is sent.
If an article has more than one distribution specified, then each one
is according to the above rules. If any of the specified distributions
indicate that the article should be sent, it is; if none do, it is not
sent — the rules are used as a ‘‘logical or.’’ It is almost definitely
a mistake to have a single feed that specifies distributions that start
with an exclamation point along with some that don’t.
Distributions are text words, not patterns; entries like ‘‘*’’ or
‘‘all’’ have no special meaning.
The flags parameter specifies miscellaneous parameters. They may be
specified in any order; flags that take values should have the value
immediately after the flag letter with no whitespace. The valid flags
are:
<size An article will only be sent to the site if it is less than size
bytes long. The default is no limit.
>size An article will only be sent to the site if it is greater than
size bytes long. The default is no limit.
Achecks
An article will only be sent to the site if it meets the
requirements specified in the checks, which should be chosen
from the following set:
d Distribution header required
p Do not check Path header for the sitename before
propagating (the exclusions are still checked).
Bhigh/low
If a site is being fed by a file, channel, or exploder (see
below), the server will normally start trying to write the
information as soon as possible. Providing a buffer may give
better system performance and help smooth out overall load if a
large batch of news comes in. The value of the this flag should
be two numbers separated by a slash. The first specifies the
point at which the server can start draining the feed’s I/O
buffer, and the second specifies when to stop writing and begin
buffering again; the units are bytes. The default is to do no
buffering, sending output as soon as it is possible to do so.
Fname This flag specifies the name of the file that should be used if
it is necessary to begin spooling for the site (see below). If
name is not an absolute pathname, it is taken to be relative to
/var/spool/news/out.going. Then, if the destination is a
directory, the file togo in that directory will be used as
filename.
Gcount If this flag is specified, an article will only be sent to the
site if it is posted to no more than count newsgroups.
Hcount If this flag is specified, an article will only be sent to the
site if it has count or fewer sites in its Path line. This flag
should only be used as a rough guide because of the loose
interpretation of the Path header; some sites put the poster’s
name in the header, and some sites that might logically be
considered to be one hop become two because they put the posting
workstation’s name in the header. The default value for count
is one.
Isize The flag specifies the size of the internal buffer for a file
feed. If there are more file feeds then allowed by the system,
they will be buffered internally in least-recently-used order.
If the internal buffer grows bigger then size bytes, however,
the data will be written out to the appropriate file. The
default value is (16 * 1024) bytes.
Nmodifiers
The newsgroups that a site receives are modified according to
the modifiers, which should be chosen from the following set:
m Only moderated groups
u Only unmoderated groups
Ssize If the amount of data queued for the site gets to be larger than
size bytes, then the server will switch to spooling, appending
to a file specified by the ‘‘F’’ flag, or
/var/spool/news/out.going/sitename if the ‘‘F’’ flag is not
specified. Spooling usually happens only for channel or
exploder feeds.
Ttype This flag specifies the type of feed for the site. Type should
be a letter chosen from the following set:
c Channel
f File
l Log entry only
m Funnel (multiple entries feed into one)
p Program
x Exploder
Each feed is described below in the section on feedtypes. The
default is Tf.
Witems If a site is fed by file, channel, or exploder, this flag
controls what information is written. If a site is fed by a
program, only the asterisk (‘‘*’’) has any effect. The items
should be chosen from the following set:
b Size of the article in bytes
f Article’s full pathname
g The newsgroup the article is in;
if cross-posted, then the first of the groups this
site gets
m Article’s Message-ID
n Article’s pathname relative to the spool directory
p The time the article was posted as seconds since epoch.
s The site that fed the article to the server;
from the Path header
t Time article was received as seconds since epoch
* Names of the appropriate funnel entries;
or all sites that get the article
D Value of the Distribution header;
? if none present
H All headers
N Value of the Newsgroups header
O Overview data
R Information needed for replication
P Path header information needed for inpaths
More than one letter can be used; the entries will be separated
by a space, and written in the order in which they are
specified. The default is Wn.
The ‘‘H’’ and ‘‘O’’ items are intended for use by programs that
create news overview databases. If ‘‘H’’ is present, then the
all the article’s headers are written followed by a blank line.
An Xref header (even if one does not appear in the filed
article) and a Bytes header, specifying the article’s size, will
also be part of the headers. If used, this should be the only
item in the list; if preceeded by other items, however, a
newline will be written before the headers. The ‘‘O’’ generates
input to the overchan(8) program. It, too, should be the only
item in the list.
The asterisk has special meaning. It expands to a space-
separated list of all sites that received the current article.
If the site is the target of a funnel however (i.e., it is named
by other sites which have a ‘‘Tm’’ flag), then the asterisk
expands to the names of the funnel feeds that received the
article. If the site is fed by a program, then an asterisk in
the param field will be expanded into the list of funnel feeds
that received the article. A site fed by a program cannot get
the site list unless it is the target of other ‘‘Tm’’ feeds.
The interpretation of the param field depends on the type of feed, and
is explained in more detail below in the section on feedtypes. It can
be omitted.
The site named ME is special. There should only be one such entry, and
it should be the first entry in the file. If the ME entry has a
subscription list, then that list is automatically prepended to the
subscription list of all other entries. For example,
‘‘*,!control,!junk,!foo.*’’ can be used to set up the initial
subscription list for all feeds so that local postings are not
propagated unless ‘‘foo.* explicitly appears in the site’s subscription
list. Note that most subscriptions should have ‘‘!junk,!control’’ in
their pattern list; see the discussion of ‘‘control messages’’ in
innd(8). (Unlike other news software, it does not affect what groups
are received; that is done by the active(5) file.)
If the ME entry has a distribution subfield, then only articles that
match the distribution list are accepted; all other articles are
rejected. A commercial news server, for example, might have
‘‘/!local’’ to reject local postings from other, misconfigured, sites.
FEEDTYPESInnd provides four basic types of feeds: log, file, program, and
channel. An exploder is a special type of channel. In addition,
several entries can feed into the same feed; these are funnel feeds,
that refer to an entry that is one of the other types. Note that the
term ‘‘feed’’ is technically a misnomer, since the server does not
transfer articles, but reports that an article should be sent to the
site.
The simplest feed is one that is fed by a log entry. Other than a
mention in the news logfile, no data is ever written out. This is
equivalent to a ‘‘Tf’’ entry writing to /dev/null except that no file
is opened.
A site fed by a file is simplest type of feed. When the site should
receive an article, one line is written to the file named by the param
field. If param is not an absolute pathname, it is taken to be
relative to /var/spool/news/out.going. If empty, the filename defaults
to /var/spool/news/out.going/sitename. This name should be unique.
When a site fed by a file is flushed (see ctlinnd), the following steps
are performed. The script doing the flush should have first renamed
the file. The server tries to write out any buffered data, and then
closes the file. The renamed file is now available for use. The
server will then re-open the original file, which will now get created.
A site fed by a program has a process spawned for every article that
the site receives. The param field must be a sprintf(3) format string
that may have a single %s parameter, which will be given a pathname for
the article, relative to the news spool directory. The full path name
may be obtained by prefixing the %s in the param field by the news
spool directory prefix. Standard input will be set to the article or
/dev/null if the article cannot be opened for some reason. Standard
output and error will be set to the error log. The process will run
with the user and group ID of the /var/run/innd directory. Innd will
try to avoid spawning a shell if the command has no shell meta-
characters; this feature can be defeated by appending a semi-colon to
the end of the command. The full pathname of the program to be run
must be specified; for security, PATH is not searched.
If the entry is the target of a funnel, and if the ‘‘W*’’ flag is used,
then a single asterisk may be used in the param field where it will be
replaced by the names of the sites that fed into the funnel. If the
entry is not a funnel, or if the ‘‘W*’’ flag is not used, then the
asterisk has no special meaning.
Flushing a site fed by a program does no action.
When a site is fed by a channel or exploder, the param field names the
process to start. Again, the full pathname of the process must be
given. When the site is to receive an article, the process receives a
line on its standard input telling it about the article. Standard
output and error, and the user and group ID of the all sub-process are
set as for a program feed, above. If the process exits, it will be
restarted. If the process cannot be started, the server will spool
input to a file named /var/spool/news/out.going/sitename. It will then
try to start the process some time later.
When a site fed by a channel or exploder is flushed, the server closes
down its end of the pipe. Any pending data that has not been written
will be spooled; see the description of the ‘‘S’’ flag, above. No
signal is sent; it is up to the program to notice EOF on its standard
input and exit. The server then starts a new process.
Exploders are a superset of channel feeds. In addition to channel
behavior, exploders can be sent command lines. These lines start with
an exclamation point, and their interpretation is up to the exploder.
The following messages are generated automatically by the server:
newgroup group
rmgroup group
flush
flush site
These messages are sent when the ctlinnd command of the same name is
received by the server. In addition, the ‘‘send’’ command can be used
to send an arbitrary command line to the exploder child-process. The
primary exploder is buffchan(8).
Funnel feeds provide a way of merging several site entries into a
single output stream. For a site feeding into a funnel, the param
field names the actual entry that does the feeding.
For more details on setting up different types of news feeds, see the
INN installation manual.

EXAMPLES

## Initial subscription list and our distributions.
ME:*,!junk,!foo.*/world,usa,na,ne,foo,ddn,gnu,inet\
::
## Feed all moderated source postings to an archiver
source-archive!:!*,*sources*,!*wanted*,!*.d\
:Tc,Wn:/usr/lib/news/bin/archive -f -i \
/usr/spool/news.archive/INDEX
## Watch for big postings
watcher!:*\
:Tc,Wbnm\
:exec awk ’$1 > 1000000 { print "BIG", $2, $3 }’ >/dev/console
## A UUCP feed, where we try to keep the "batching" between 4 and 1K.
ihnp4:/world,usa,na,ddn,gnu\
:Tf,Wnb,B4096/1024:
## Usenet as mail; note ! in funnel name to avoid Path conflicts.
## Can’t use ! in "fred" since it would like look a UUCP address.
fred:!*,comp.sources.unix,comp.sources.bugs\
:Tm:mailer!
barney@bar.com:!*,news.software.nntp,comp.sources.bugs\
:Tm:mailer!
mailer!:!*\
:W*,Tp:/usr/ucb/Mail -s "News article" *
## NNTP feeds fed off-line via nntpsend or equivalent.
feed1::Tf,Wnm:feed1.domain.name
peer.foo.com:foo.*:Tf,Wnm:peer.foo.com
## Real-time transmission.
mit.edu:/world,usa,na,ne,ddn,gnu,inet\
:Tc,Wnm:/usr/lib/news/bin/nntplink -i stdin mit.edu
## Two sites feeding into a hypothetical NNTP fan-out program:
nic.near.net:\
:Tm:nntpfunnel1
uunet.uu.net/uunet:!ne.*/world,usa,na,foo,ddn,gnu,inet\
:Tm:nntpfunnel1
nntpfunnel1:!*\
:Tc,Wmn*:/usr/lib/news/bin/nntpfanout
## A UUCP site that wants comp.* and moderated soc groups
uucpsite!comp:!*,comp.*/world,usa,na,gnu\
:Tm:uucpsite
uucpsite!soc:!*,soc.*/world,usa,na,gnu\
:Tm,Nm:uucpsite
uucpsite:!*\
:Tf,Wnb:/usr/spool/batch/uucpsite
The last two sets of entries show how funnel feeds can be used. For
example, the nntpfanout program would receive lines like the following
on its standard input:
<123@litchi.foo.com> comp/sources/unix/888 nic.near.net uunet.uu.net
<124@litchi.foo.com> ne/general/1003 nic.near.net
Since the UUCP funnel is only destined for one site, the asterisk is
not needed and entries like the following will be written into the
file:
<qwe#37x@snark.uu.net> comp/society/folklore/3
<123@litchi.foo.com> comp/sources/unix/888

HISTORY

Written by Rich $alz <rsalz@uunet.uu.net> for InterNetNews. This is
revision 1.35, dated 1996/12/17.